Directed the scribing of precision compass dial, a bit map CAD system improves the usability of the scriber. By increasing resolving power of the bit map (pixels/mm), the precesion of pattern is improved. The pattern design is displayed on the screen and it is converted into scribing information and then converted into scribing control data by NC. The scribing process can be simulated by the computer and the scaling precision of the workpiece can be judged.